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SurlySingle Cog - Steel


Item # SRY0001

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  • 13t, 3/32 ($30.00)
  • 14t, 3/32 ($30.00)
  • 15t, 3/32 ($30.00)
  • 16t, 3/32 ($30.00)
  • 17t, 3/32 ($30.00)
  • 18t, 3/32 ($30.00)
  • 19t, 3/32 ($30.00)
  • 20t, 3/32 ($30.00)
  • 21t, 3/32 ($30.00)
  • 22t, 3/32 ($30.00)
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Item # SRY0001

Fewer gears more beers.

Sometimes you need a smaller cog, sometimes a bigger one; luckily, the Surly Single Cog caters to your fancy. The machined SCM415 Cro-Moly steel cog features a tall tooth profile to prevent chain skip and work with 6-9-speed 3/32in chains.

  • Available in every increment from 13-22T for perfect gearing\
  • Stackable and derailleur compatible for a multi-speed drivetrain
  • 8- or 9-speed chain recommended but will work with 6- and 9-speed 3/32in chains
  • Heat-treated for ultimate strength
  • Chrome-plated for surface hardening and improved chain lubricity
  • Fits Shimano-compatible freehub bodies
Tech SpecsWeight
Tech Specs
SCM415 CroMoly steel
Recommended Use
single speed
Manufacturer Warranty
1 year

Actual Weight

Actual weights are measured in-house by the Competitive Cyclist team.

Have questions? Chat with a Gearhead



13t, 3/32
14t, 3/32
15t, 3/32
16t, 3/32
17t, 3/32
18t, 3/32
19t, 3/32
20t, 3/32
21t, 3/32
22t, 3/32

Reviews & Community


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Great Cog for all your SS Activities

  • Familiarity: I've put it through the wringer

I had my bikepacking rig set up SS while in Wisconsin's flatlands this summer. The Surly cog served me well over many weekend trips on a loaded bike. It's been fairly durable so far, and looking forward to another season of use.

Good, Not Best

  • Familiarity: I've used it several times

Steel cog that should last you forever. I use it with a 10sp chain and it works great. I love the size variety Surly gives to really dial in the perfect ratio but it did fall flat on me with a few points. The freehub body is wide, measured at 4.35mm which is certainly a step up from stealing cogs from your old cassette but doesn't measure up to the 6.3mm of the Kick Ass Cog also available at Competitive. Likewise, there is slight fore/aft play on the freehub body which is not ideal considering how tight the Kick Ass Cog fits. Conclusion: If you're trying to stick to budget, the Surly is a great piece that should last a long time. If you don't mind the premium, go with the precision of the Kick Ass Cog.

Great Cog!

  • Familiarity: I've used it several times

I put the 17T cog on my Surly Krampus with 32T up front. It's a good gear for pushing up single track hills and mountain biking but I would look for a more stout ratio on the road!

IT it's a tank!

  • Familiarity: I've put it through the wringer

This monster is bomb proof, at this rate it will outlast the bike.
Not the lightest, but it's steel and great for the price.

I'll have another!

  • Familiarity: I've put it through the wringer

I guess you can say Surly is starting to grow on me... This is my 3rd Surly cog within the last couple years. I've got a 16t and an 18t and I love them to death, except when it comes to some of the more hill filled courses. I needed something not so tall, so I snagged the 20t this time around. Five minutes later, I am rollin' a tad easier on up the hills. I'd like to say the 20t helps out just a wee bit more, but on a SSCX bike, it's all pure pain; we'lll see how this season goes.

These things can really take some abuse. Like mud and snow crunchy munchy abuse. My cross bike is steel, so I figured I'd stick with the theme and keep the cogs steel as well. I've had friends run some aluminum cogs and after just one season, their stuff is usually mangled and toothless.

PS. These things are nicely priced!

Great Cog

  • Familiarity: I've put it through the wringer

This is one of the best SS cassette cogs on the market. It's tough and nicely machined. Weight is reasonable (though if you're that concerned then you're being silly). It's steel (as any SS cog should be) and wears almost negligibly.

What makes this better than most is the wide base (4mm) that does not chew up cassette freehub bodies, not even lightweight alu or Ti ones. If you have XTR hubs with the Ti freehub body, this is a must. There are others (Niner, CK) that have this as well, but they're much more expensive.

On top of all of that, it looks good. The larger cogs have nicely spaced drilled holes that probably shave negligible weight but just look cool. The blasted finish is nice and even and well done.

The weights (measured) of the cogs I have:

17T: 53g

18T: 59g

19T: 70g

20T: 77g

21T: 87g


    I put the 22t on my new single speed because the one I had was kicking my ass and it's a great improvement for my weakness. It's a solid gear for climbing and keeping a good pace on level ground, not to mention it's a burly little guy.

    Out lasts everything.

      I love this cog and I have tried everything out. Some have work well for a while and some will bend or snap after a week. This Surly Single Cog is how all bike components should be made, to with stand the test of time. They have a wider base that keeps your freehub body in perfect shape. You can also find a perfect chain line with out moving to much. Just flip it over for 4mm inside or outside, spacer kits sometime don't have one small enough for that fine tune adjustment. These cogs have a tall tooth profile that is essential for preventing chain skip from the extra torque from a single speed drivetrain. Another thing I love about the cog base width is 4.35mm, so I stack a 4 of them up and use a 9-speed shifter for a slop style/ free ride set up. And I have never had my chain fall off and I mean never. Spend a little more now and save a ton in the long ride.

      Out lasts everything.

      Why are these cogs meant to fit 8 or 9...

      Why are these cogs meant to fit 8 or 9 speed chains, aren't these cogs usually used for SS? Will they work with a single speed chain?

      1/2x1/8" chains vs. 1/2x3/32" chains. 1/2x1/8" chains suck. Run whatever you want, but bigger isn't better here. Yeah, they're wider, but according to manufacturer-supplied data, they're not stronger and they are definitely not of better quality. Multi-speed drivetrains is where the bucks are at, and chains that work on such drivetrains are where the manufacturers of chains showcase their innovations and developments in quality. The rollers are better, the plates are better, the pins are stronger, and the construction method (riveting procedure) is better on all multi-speed 3/32" chains. I guess if you grind your chainring and chain down the handrail every night at the local pub, a bigger 1/2x1/8 " chain will last longer, but most of us don't and it won't. If you have an old Singleator: Dammit, don't use a 1/2x1/8" chain!!! Otherwise, you'll tear the Singleator off the bike, among other things, guaranteed. This is no longer the case with our redesigned Singleator. The old version used a loop over the jockey wheel to help keep the chain in place. This loop would catch 1/8" chains, which are fatter than 3/32". The current Singleator uses guide plates on each side of the jockey wheel to achieve the same purpose, but depending on the orientation of the wheels, it can run 3/32" or 1/8" chains. We still prefer narrow chains, but if you absolutely must use an 1/8", the new design will work for you.

      Bullet Proof

        Been riding with these Surly cogs for over 3 years. I have three of them ~ 16 tooth, 18, and 20. I swap them out before a ride depending on the terrain I'll be on. The wider base of the gear does exactly what it's claimed to do. There are no signs of wear or damage on my freehub, and the cogs themselves still look as good as when I first bought them.

        To be honest, I never noticed if they were heavy or not. After all, it is only one cog compared to an entire cassette. Only a weight weenie would take issue with these cogs. Everyone else will be pleased with the long life and no damage to the splines on their freehubs.


          I'm not necessarily a weight weenie but even I couldn't but this thing on my bike. Felt like a brick compared to my CK 20t. I know the CK is a little smaller. Went with the Niner 22t instead.

          What makes a brick is in the eye of the beholder. At 20T, the Surly weighs 77g while the CK weighs 52g. At 19T it's 70g/48g, at 18T it's 59g/52g, and at 17T it's 53g/35g. The CK is 20-25g lighter depending on the cog size; it's also steel and has a wide cassette stance and lasts pretty much forever, so it really comes down to whether one thinks the 20-25g and CK bling factor is worth the extra $20. I have a Surly bike and chainring, so for me the Surly cogs match better, otherwise that CK would be really tempting.

          The Niner is either alu or Ti, so while it's much lighter it also wears much, much faster. A friend of mine wear through a Niner alu cog once per race season whereas my Surly cogs never show any wear.